package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.alibaba.fastjson.JSON;
import com.baomidou.mybatisplus.extension.service.IService;
import com.hmdp.dto.Result;
import com.hmdp.entity.RedisData;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisConstants;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 * 服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;

    @Override
    public Result queryById(Long id) {
//        h缓存穿透
//        Shop shop = queryWithPassThrought(id);
//互斥锁解决缓存击穿
//        Shop shop = queryWithMutex(id);
//        Shop shop = queryWithLogicalExpire(id);

//         解决缓存穿透
//        Shop shop = cacheClient
//                .queryWithPassThrough
//                 (CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);

        // 互斥锁解决缓存击穿
         Shop shop = cacheClient
                 .queryWithMutex
                 (CACHE_SHOP_KEY, id, Shop.class, this::getById, CACHE_SHOP_TTL, TimeUnit.MINUTES);
//
//      逻辑过期解决缓存击穿
//         Shop shop = cacheClient
//                 .queryWithLogicalExpire
//                 (CACHE_SHOP_JCEP_KEY, id, Shop.class, this::getById, 60L, TimeUnit.SECONDS);

        if (shop == null) {
            return Result.fail("店铺不存在");
        }
        return Result.ok(shop);
    }

    /*
     * 逻辑过期解决缓存击穿问题缓存击穿*/
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public Shop queryWithLogicalExpire(Long id) {
        String key = CACHE_SHOP_JCEP_KEY + id;
        // 1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        // 2.判断是否存在
        if (StrUtil.isBlank(json)) {
            // 3.存在，直接返回
            return null;
        }
        // 4.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        // 5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            // 5.1.未过期，直接返回店铺信息
            return shop;
        }
        // 5.2.已过期，需要缓存重建
        // 6.缓存重建
        // 6.1.获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        // 6.2.判断是否获取锁成功
        if (isLock) {
//            避免多线程有线程已经执行到 5.2. 避免不必要的key再次重建  在检验一次过期时间
            // 1.从redis查询商铺缓存
            json = stringRedisTemplate.opsForValue().get(key);
            // 2.判断是否存在
            if (StrUtil.isBlank(json)) {
                // 3.存在，直接返回
                return null;
            }
            // 4.命中，需要先把json反序列化为对象
            redisData = JSONUtil.toBean(json, RedisData.class);
            shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
            expireTime = redisData.getExpireTime();
            // 5.判断是否过期
            if (expireTime.isAfter(LocalDateTime.now())) {
                // 5.1.未过期，直接返回店铺信息
                return shop;
            }
            CACHE_REBUILD_EXECUTOR.submit(() -> {

                try {
                    //重建缓存
                    this.saveShop2Redis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    unlock(lockKey);
                }
            });
        }
        // 6.4.返回过期的商铺信息
        return shop;
    }

    public void saveShop2Redis(Long id, Long expireSeconds) {
        Shop shop = getById(id);
        try {
            Thread.sleep(200);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
//        写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_JCEP_KEY+id, JSONUtil.toJsonStr(redisData));
    }

    /*
     * 互斥锁解除缓存击穿*/
    private Shop queryWithMutex(Long id) {
        String s = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
        if (StrUtil.isNotBlank(s)) {
            Shop shop =
//                    JSONUtil.toBean(s, Shop.class);
                    JSON.parseObject(s, Shop.class);
            return shop;
        }
        if (s != null) {
//            那么只有""
            return null;

        }
        // 4.实现缓存重构

        //4.1 获取互斥锁
        String lockKey = "lock:shop:" + id;
        Shop shop = null;
        try {
            boolean lock = tryLock(lockKey);
            // 4.2 判断否获取成功
            if (!lock) {
                //4.3 失败，则休眠重试
                Thread.sleep(50);
                queryWithMutex(id);
            }
            //4.4 成功， 再次判断是否有缓存 根据id查询数据库
            s = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
            if (StrUtil.isNotBlank(s)) {
                shop =
//                    JSONUtil.toBean(s, Shop.class);
                        JSON.parseObject(s, Shop.class);
                return shop;
            }
            shop = getById(id);
            // 5.不存在，返回错误
            if (shop == null) {
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id,
                        "", RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
                //返回错误信息
                return null;
            }
            //6.写入redis
            stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id,
                    //                JSONUtil.toJsonStr(shop)
                    JSON.toJSONString(shop)
                    , CACHE_SHOP_TTL
                    , TimeUnit.MINUTES
            );

        } catch (InterruptedException e) {
            throw new RuntimeException();
        } finally {
            //7.释放互斥锁
            unlock(lockKey);
        }
        return shop;
    }

    /*
     * 缓存穿透*/
    private Shop queryWithPassThrought(Long id) {
        String s = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
        if (StrUtil.isNotBlank(s)) {
            Shop shop =
//                    JSONUtil.toBean(s, Shop.class);
                    JSON.parseObject(s, Shop.class);
            return shop;
        }
        if (s != null) {
//            那么只有""
            return null;

        }
        Shop shop = getById(id);
        if (shop == null) {
            stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id,
                    "", RedisConstants.CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id,
//                JSONUtil.toJsonStr(shop)
                JSON.toJSONString(shop)
                , CACHE_SHOP_TTL
                , TimeUnit.MINUTES
        );
        return shop;
    }

    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺id不能为空");
        }
//        更新数据库
        updateById(shop);

//        删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);

        return Result.ok();
    }
}
